Dual Fillet Welding Methods And Systems

ABSTRACT

A system and method of hybrid welding a dual fillet weld. The system includes a laser system that leads a first torch and preheats at least one workpiece. The system also includes a first welding power supply that supplies a first welding waveform to a first wire via the first torch. The first welding waveform creates a first arc between the first wire and the at least one workpiece. The system further includes a second welding power supply that supplies a second welding waveform to a second wire via a second torch. The second welding waveform creates a second arc between the second wire and the at least one workpiece. A controller in the system is operatively coupled to the first power supply, the second power supply and the laser system. The controller synchronizes the first welding waveform and the second welding waveform such that welding current pulses of the second welding waveform at the second torch are not in phase with welding current pulses of the first welding waveform at the first torch. The system is set up such that the first arc and the second arc are across from each other on opposite sides of a weld.

PRIORITY

The present application is a continuation-in-part of and claims priorityto U.S. patent application Ser. Nos. 11/457,609 filed Jul. 14, 2006 and12/254,067 filed Oct. 20, 2008, which is incorporated herein byreference in its entirety

FIELD OF THE INVENTION

The present invention relates generally to arc welding, and moreparticularly to methods and systems for creating dual fillet welds usingsynchronized welding waveforms and modulated workpoints.

BACKGROUND

In welding fabrications, the “T” connection or T-joint is one of themost common welded connections used to join two pieces of metaltogether, in which a first piece of metal such as a stiffener workpieceforms the leg of the T and the second workpiece is the top of the T.Often, both corners of the T connection are welded with fillet welds,wherein these weld joints are referred to as “dual fillet” welds. Insome applications, the joint is long and straight and the welding can bemechanized with a pair of welding torches fixtured on a common frameworkfacing both corners of the T connection and both welds are performedconcurrently to reduce fabrication time. A common example of dual filletwelding is in the fabrication of girders, in which stiffeners areattached to the web of a girder with two long straight fillet welds.Other examples include T connections on round fabrications, such asconnection of stiffeners to a tube or pipe, wherein the tube is rotatedand a mechanized welding fixture makes both welds at the corners of theT at the same time. Yet another example of this technology uses a tubeas the top of the T and a plate as the leg of the T. In all of theseexamples, both fillet welds at the corners of a T connection are weldedat the same time. Depending on the application, fabricators can use manyvarious arc welding processes including SAW, FCAW-S, FCAW-G, MCAW, orGMAW. With all of the processes listed, the welding procedure (e.g.,amps, volts, travel speed, etc.) is closely controlled to achieve thedesired weld bead and penetration level. Due to the concurrent welding,however, the high heat and magnetic field from the arc on one side ofthe joint will often adversely affect the arc and weld puddle on theother side. Typically fabricators are forced to reduce weldingprocedures to overcome the problems associated with two arcs operatingon either side of a T connection. Thus there is a need for improvedwelding systems and techniques by which high quality welds can bedeposited on both sides of a T connection simultaneously.

SUMMARY

The invention is related to dual fillet welding and improved methods andapparatus therefor. The following is a summary of one or more aspects ofthe invention to facilitate a basic understanding thereof, where thesummary provided below is not an extensive overview of the invention,and is neither intended to identify certain elements of the invention,nor to delineate the scope of the invention. Rather, the primary purposeof the summary is to present some concepts of the invention in asimplified form prior to the more detailed description that is presentedhereinafter. Improved welding systems and methods are provided in whichfirst and second fillet welds are created with synchronized waveformsand/or workpoints to facilitate uniform controllable weld penetration,shape, and size, where the advances presented herein may facilitatecreation of consistent high quality dual fillet welds.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description and drawings set forth certain illustrativeimplementations of the invention in detail, which are indicative ofseveral exemplary ways in which the principles of the invention may becarried out. Other objects, advantages and novel features of theinvention will become apparent from the following detailed descriptionof the invention when considered in conjunction with the drawings, inwhich:

FIG. 1A is a simplified system diagram showing an exemplary weldingsystem with synchronized welding machines for creating a dual filletweld according to one or more aspects of the present invention; FIG. 1Bis a detailed system diagram illustrating further details of the weldingsystem of FIG. 1A in accordance with one or more aspects of theinvention;

FIG. 2A is sectional end view taken along line 2-2 in FIG. 1Billustrating an exemplary solid electrode that may be used for dualfillet welding with the system of FIGS. 1A and 1B;

FIG. 2B is another sectional view taken along line 2-2 in FIG. 1Billustrating an exemplary cored electrode that may be used in the systemof FIG. 1B for dual fillet welding;

FIG. 3 is a partial top plan view showing an exemplary dual filletwelding process using the system of FIGS. 1A and 1B;

FIG. 4 is a partial end elevation view in section taken along line 4-4of FIG. 3 illustrating molten weld material during formation of the dualfillet weld;

FIG. 5 is a partial end elevation view in section taken along line 5-5of FIG. 3 illustrating a cooled dual fillet weld;

FIG. 6 is an enlarged sectional elevation view showing further detailsof an exemplary fillet weld created using the system of FIGS. 1A and 1B;

FIG. 7A is a graph showing exemplary plots of first and secondsynchronized DC pulse welding current waveforms provided by the powersources in the system of FIGS. 1A and 1B for substantially in-phaseside-to-side welding waveforms with about zero degree waveform phaseangle;

FIG. 7B is a graph showing exemplary DC pulse welding current waveformswith a controlled non-zero degree waveform phase angle;

FIG. 7C is a graph showing exemplary plots of synchronized DC pulsecurrent waveforms in the system of FIGS. 1A and 1B for substantiallyout-of-phase welding waveforms with about 180 degree waveform phaseangle;

FIG. 7D is a graph showing exemplary plots of synchronized square-wavetype welding machine wire feed speed and power source output workpointvalue waveforms in the system of FIGS. 1A and 1B for substantiallyout-of-phase machine operation at a workpoint phase angle of about 180degrees;

FIG. 7E is a graph showing exemplary plots of synchronized rounded wirefeed speed and power source output workpoint value waveforms in thesystem of FIGS. 1A and 1B at a workpoint phase angle of about 180degrees;

FIG. 7F is a graph showing exemplary plots of synchronized ramped wirefeed speed and power source output workpoint value waveforms in thesystem of FIGS. 1A and 1B at a workpoint phase angle of about 180degrees;

FIG. 7G is a graph showing exemplary plots of synchronized sinusoidalwire feed speed and power source output workpoint value waveforms in thesystem of FIGS. 1A and 1B at a workpoint phase angle of about 180degrees;

FIG. 8 is a system level schematic diagram illustrating further detailsof the welding system of FIGS. 1A and 1B, with the welding machines anda travel controller being synchronized and controllable in synergicfashion according to a user selected process and a system workpoint,wherein with the welding torches are controllably movable by a travelmechanism relative to stationary workpieces;

FIG. 8A is a system level schematic diagram illustrating an alternatetravel mechanism configuration with the workpieces being movablerelative to stationary welding torches;

FIG. 9 is a simplified schematic diagram illustrating further details ofone of the exemplary switching type welding power sources providing awelding current according to a pulse width modulated switching signalfrom a programmable waveform generation system;

FIG. 10 is a partial top plan view showing an exemplary dual filletsubmerged arc welding operation using the system of FIGS. 1A and 1B withsynchronized AC welding waveforms;

FIG. 11 is a partial end elevation view in section taken along line11-11 of FIG. 10 illustrating molten weld material and slag being formedwithin a bed of granular flux during submerged arc dual fillet welding;

FIG. 12 is a partial end elevation view in section taken along line12-12 of FIG. 10 illustrating a cooled dual fillet weld with solidifiedslag overlying the welds;

FIG. 13 is a sectional end elevation view showing the dual filletsubmerged arc weld following slag removal;

FIG. 14A is a plot showing graphs of substantially in-phase first andsecond AC welding waveforms provided by the power sources in thesubmerged arc dual fillet welding operation of FIGS. 10-12;

FIG. 14B is a graph showing exemplary AC welding current waveforms witha controlled non-zero degree waveform phase angle;

FIG. 14C is a graph showing exemplary plots of synchronized AC pulsecurrent waveforms in the system of FIGS. 1A and 1B for substantiallyout-of-phase welding waveforms with about 180 degree waveform phaseangle;

FIG. 14D is a graph showing exemplary plots of synchronized square-wavetype welding machine wire feed speed, power source output, and weldingfrequency workpoint value waveforms in the system of FIGS. 1A and 1B forsubstantially out-of phase machine operation at a workpoint phase angleof about 180 degrees;

FIG. 15A is a partial end elevation view in section illustrating anexemplary beveled stiffener first workpiece used in forming a dualfillet welded T-joint;

FIG. 15B is a partial end elevation view of the workpieces of FIG. 15Afollowing dual fillet welding to create a complete penetration dualfillet weld joint using the synchronized welding methods and systems ofthe invention;

FIG. 16A illustrates an exemplary embodiment of the present invention ina hybrid laser application;

FIG. 16B illustrates a top view of the system in FIG. 16A; and

FIG. 17 illustrates an exemplary controller for the system in FIG. 16A.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures, several embodiments or implementations ofthe present invention are hereinafter described in conjunction with thedrawings, wherein like reference numerals are used to refer to likeelements throughout and wherein the illustrated structures are notnecessarily drawn to scale. Although several preferred embodiments areillustrated and described hereinafter in the context of root pass dualfillet welding using two welding electrodes positioned on opposite sidesof a welded workpiece, other embodiments are possible in which two ormore pairs of opposing welding electrodes are used in creating a dualfillet weld with one or more passes, with the waveforms applied to theelectrodes and/or the workpoints used by opposing welding machines of agiven pair being operated in a synchronized manner to provide controlledwaveform and/or workpoint phase angles during concurrent creation of twofillet welds. Further embodiments are also contemplated in which severalpasses can be used to form a dual fillet weld, with the welding signalwaveforms and/or workpoint waveforms being temporally synchronized suchthat the signals used in forming the welds on either side of the T-jointare provided at a controllable phase relationship to one another. Inthis regard, the specific embodiments illustrated and describedhereinafter are not intended as limitations, but rather as examples ofone or more possible preferred implementations of the various aspects ofthe invention.

FIGS. 1A and 1B show an exemplary dual fillet welding apparatus orsystem 2 including first and second welding machines 20 a and 20 b witha synchronizing controller 40 providing for control of the phaserelationship of either or both of the welding current waveforms and/orone or more machine workpoints in creating dual fillet welds W1 and W2using electrodes E1 and E2 and welding arcs A1 and A2, respectively toweld a first workpiece WP1 to a second workpiece WP2. As shown in FIG.1B, the synchronizing controller may be provided in a welding systemcontroller 10 for performing a DC pulse dual fillet welding processusing flux cored welding electrodes E1 and E2, an AC submerged arcwelding (SAW) process using solid welding electrodes E1 and E2 or othersuitable dual fillet welding process using solid or cored electrodeswith or without external shielding gas GS1, GS2. The selected weldingprocess is performed to create the first and second fillet welds W1 andW2, respectively, on opposite sides of a T-joint formed by an end of thefirst workpiece WP1, such as a stiffener, and a flat surface of thesecond workpiece WP2, where the workpieces WP and the resulting T-jointmay be flat, but can also be curved. The welding machines 20 in theexemplary system 2 are generally similar to one another, althoughdifferent machines may be used in other implementations. The firstmachine 20 a includes a power source 24 a having an output terminal 25 acoupled to provide a waveform controlled welding signal (weldingvoltage, current) to the corresponding electrode E1 in order to createthe first dual fillet weld W1. As illustrated and described furtherbelow with respect to FIG. 9, the exemplary power source 24 a is aswitching type source including an output stage that provides a weldingsignal according to one or more pulse width modulated switching signalscreated by a waveform generator that controls a pulse width modulator inthe power source 24 a, where the exemplary sources 24 of system 2 aregenerally of the type shown in Blankenship U.S. Pat. No. 5,278,390 andHsu U.S. Pat. No. 6,002,104 incorporated by reference above and as soldby the Lincoln Electric Company under the trademark POWER WAVE. Themachine 20 a further includes a motorized wire feeder 26 a operable tofeed or direct the electrode E1 toward a first side of the weld joint ata controlled wire feed speed via a motor M1 driving one or more driverolls 27 a, whereby electrode wire E1 is delivered from a spool or othersupply 29 a to the weld W1. The second machine 20 b is similarlyconfigured, including a second power source 24 b having an output stagewith an output terminal 25 b that is coupled to a second weldingelectrode E2 and provides a second welding current signal thereto with asecond waveform generated by a waveform generator controlling a pulsewidth modulator circuit to determine the current operation of the outputstage. The second machine 20 b also includes a wire feeder 26 b with amotor M2 driving rolls 27 b to direct the electrode E2 from a supplyreel 29 b toward a second side of the weld joint at a second wire feedspeed. The power source output terminals 25 a and 25 b are electricallycoupled, directly or indirectly, to the respective welding electrodes E1and E2 using any suitable electrical contact or interconnectionstructures, wherein these connections are shown schematically in FIG. 1for ease of illustration. The welding electrode wires E are fed from thesupply spools 29 through first and second welding torch nozzles N1 andN2, wherein external shielding gas may be provided to the fillet weldsthrough suitable ports and passageways within nozzles N from gassupplies GS1 and GS2, respectively, although other embodiments arepossible in which no shielding gas is used. Referring also to FIGS. 2Aand 2B, any type of welding electrodes E may be used, for example, solidelectrodes (FIG. 2A) comprising a solid electrode material 52 with orwithout an optional outer coating 51. Another suitable electrode E isshown in FIG. 2B, in this case a cored type electrode E having ametallic outer sheath 54 surrounding an inner core 56, where the core 56includes granular and/or powder flux material for providing a shieldinggas and protective slag to protect a molten weld pool during the dualfillet welding, as well as alloying materials to set the materialcomposition of the fillet weld material. The dual fillet weld processingshown in FIGS. 1A, 1B, and 8 is used to weld the stiffener workpiece WP1to the flat upper surface of the second workpiece WP2, wherein twowelding arcs A1 and A2 are provided by the first and second machines 20a and 20 b, respectively, on opposite sides of the stiffener workpieceWP1.

As best shown in FIGS. 8 and 8A, the two fillet welds are performedconcurrently from both sides to join the workpieces WP1 and WP2 as atravel mechanism 52 moves a weld fixture 30 in a horizontal direction 60(FIG. 8) or alternatively moves the workpieces WP1, WP2 on a carriage 30a relative to fixed welding torches (Fig. SA). The welding process maybe tailored to create first and second welds W1 and W2 of the same orsimilar weld size (e.g., leg size), although the methods and systems ofthe invention may be used in creating dual fillet welds with differentfirst and second weld sizes, shapes, profiles, etc.

In the example of FIGS. 1A and 1B, the machines 20 are operativelycoupled with the synchronizing controller 40 and a workpiece allocationsystem 12 of the system controller 10 for exchanging data and controlsignals, messages, data, etc. therewith. In one embodiment, astand-alone welding system controller 10 includes the synchronizingcontroller 40 operatively coupled with the power sources 24 a and 24 band provides power sources 24 with synchronization information (e.g.,signals, messages, etc.) to synchronize the first and second waveformgenerators thereof such that the first and second welding currents areat a controlled phase angle with respect to one another. The wirefeeders 26 may also be synchronized by or according to suitableinformation (data, signaling, etc.) from synchronizing controller 40and/or directly from the respective power sources 24 or otherintermediate components in order to coordinate the provision of weldingwire to the dual fillet welding process according to the current weldingwaveforms and other process conditions at a particular point in time.Similarly, the shielding gas supplies GS1, GS2 may be controlled insynchronized fashion using control apparatus of the machines 20according to synchronization information from the synchronizingcontroller 40. The exemplary system controller 10, moreover, includesthe workpoint allocation system 12 operatively coupled with the weldingmachines 20 a and 20 b, which receives a user selected system setpointor workpoint value and provides individual machine workpoint values tothe machines 20 to set a total output of the dual fillet welding system2. Such synergic control may be provided to allow a user to simply setone system workpoint value, for example, a deposition rate, weld size,wire feed speed, welding current, welding voltage, a travel speed, etc.,with the machines 20 and/or components thereof being provided with localworkpoints to achieve the desired system-wide performance. Moreover, theallocation system 12 or the synchronizing controller 40 or other systemcomponents may provide for modulation of one or more machine workpointsaccording to workpoint waveforms to provide a controlled machineworkpoint phase angle between the workpoint waveforms as describedfurther hereinafter. In other embodiments, one or both of thesynchronizing controller 40 and the workpoint allocation system 12 maybe separately housed, or may be integrated in one or more systemcomponents, such as the welding machines 20 or the power sources 24thereof, for example.

Referring also to FIGS. 3-6, 15A, and 15B, in creating the dual filletweld at the T-joint of the workpieces WP1 and WP2, it is desirable thatthe size and uniformity of the dual fillet weld, the amount ofpenetration, and the shape (concave, convex, etc.) are controllable,repeatable and uniform along the length of the weld so as to enhance thequality of the resulting joined structure. In addition, the relativeamount of similarity between the welds on opposite sides of the dualfillet weld may affect the quality of the T-joint weldment, whereininconsistent penetration and/or differences in the amount of weldpenetration on the two sides may lead to inferior joint strength,cracking, or other quality problems. Furthermore, the synchronization ofthe concurrent weld processes may facilitate the ability to economizethe amount of welding time and filler material used. As shown in FIGS.3-6, the dual fillet process is performed with the electrodes E1 and E2moving in the direction 60 relative to the workpieces WP1 and WP2, andwith electrodes E1 and E2 being fed at controlled wire feed speedstowards opposite first and second sides of the stiffener workpiece WP1,respectively. Providing synchronized waveform controlled weldingcurrents 11 and 12 to the electrodes E1 and E2 creates and maintainswelding arcs A1 and A2 between the electrodes E1 and E2, respectively,and the workpieces WP1 and WP2 or a weld pool thereon. The welding arcsA1 and A2, in turn, cause deposition of molten electrode material andpossibly melting of certain amounts the workpiece materials to formmolten welds W1 and W2 as shown in FIG. 4 as the electrodes E pass agiven location along the weld direction 60. The weld materials W1, W2eventually cool and solidify as best shown in FIG. 5, leaving thefinished dual fillet weld (or a finished single pass of a multiple passdual fillet weld). As best shown in FIG. 4, the localized heating of theworkpieces WP1 and WP2 during the welding process may cause the moltenweld material to laterally penetrate the stiffener WP1 by first andsecond lateral penetration distances 62 a and 62 b, where the lateralpenetration distances 62 may, but need not, be the same. The welds W1and/or W2 may also penetrate vertically downward into the flat uppersurface of the second workpiece WP2 by distances 63 a and 63 b,respectively, which distances may, but need not, be the same for a givenwelding process.

As shown in FIG. 5, moreover, the finished fillet welds W1 and W2 willhave certain profiles or shapes, wherein the exposed outer weld surfacesmay be convex as shown in the illustrated example, or alternatively mayhave generally flat, or concave, or curvilinear surface shapes or filletface contours. The weld sizes may be characterized by the vertical legdimensions 64 a and 64 b as well as by lateral or horizontal legdimensions 65 a and 65 b, wherein the vertical and lateral legdimensions may, but need not be the same for a given fillet weld, andwherein these size dimensions may, but need not, be the same for thefirst and second welds W1 and W2. Referring also to FIG. 6, an enlargedillustration of the first fillet weld W1 is shown. The finished weld W1has vertical and lateral leg dimensions 64 a and 65 a, respectively,which together define a theoretical throat dimension 70 extending fromthe original corner at the edge of the original first workpiece WP1 andthe surface of the original second workpiece WP2 to a line L1 betweenthe corner edges of the weld W1, where the effective weld throatdistance is the theoretical throat dimension 70 plus a throatpenetration distance 71. In the illustrated convex example, moreover,the degree of convexity can be quantized as a dimension 72 extendingfrom the theoretical line 71 to the outermost extension of the exposedface or surface of the weld W1. Referring also briefly to FIGS. 15A and15B, the vertical first workpiece WP1 may have beveled surfaces 202, 204at the end facing the second workpiece WP2. Furthermore, as shown inFIG. 15B, the welds W1 and W2 may join at a central location 200,thereby providing for a complete penetration weld joint.

Referring also to FIGS. 7A-7G, 8, and 8A, the inventors have appreciatedthat synchronized control of the welding current waveforms and/or ofwelding machine workpoint values may facilitate control over theconsistency of the above mentioned dimensional and performancecharacteristics of the first and second welds W1 and W2 in dual filletwelding where the two sides of the T-joint are welded concurrently. Inthis regard, the coordination of the applied welding signal waveforms ofthe first and second power sources 24 a and 24 b at a controlledwaveform phase angle may be advantageously employed to ensure that thedegree of penetration of the two opposing welds W1 and W2 aresubstantially the same on both sides of the first workpiece WP1 in caseswhere it is desired to have first and second welds of identicaldimensions, including the relative similarities with respect to verticalpenetrations 63, lateral penetrations 62, and the corner penetration 72as shown in FIGS. 4 and 6. In addition, providing the first and secondwelding current waveforms at a controlled phase angle is believed tocontribute to controllability of these dimensions in situations wherethe first and second welds are designed to be different. Alternativelyor in combination, controlled modulation of one or more machineworkpoint values such as power source output level, waveform frequency,wire feed speed, etc., at a controllable relative machine workpointphase angle can be employed for enhanced dual fillet welding.

While not wishing to be tied to any particular theory, it is believedthat simultaneous welding from both sides of workpiece WP1 withouttemporal coordination of the welding parameters of the two processes,even for otherwise identical welding parameter settings, can causeasymmetrical penetration, and lack of consistency in the penetrationdepths, weld shapes, etc., along the direction of electrode travel, dueto electromagnetic interaction of the material with fields created bythe currents flowing through the electrodes E and the resulting arcs Aas well as thermal affects of unsynchronized concurrent weldingprocesses on either side of the weld joint. These asymmetries and/orinconsistencies, in turn, may lead to suboptimal weld jointcharacteristics and/or performance, including susceptibility to crackingand/or corrosion, reduced joint strength, etc. Furthermore, controllablepenetration consistency in the two welds may also facilitate reductionin weld time (increased weld speed) and optimization of the amount offiller material used in dual fillet welding. In this regard, controlled,consistent penetration of the two fillet welds W1 and W2 beyond the rootmay allow smaller leg size dimensions for a given weld strengthspecification, by which increased weld travel speeds and/or reducedquantities of filler metal (electrode utilization) may be achieved toreduce welding costs.

FIG. 7A illustrates a graph showing exemplary plots 81 and 82 of firstand second synchronized DC pulse welding current waveforms,respectively, provided by the power sources 24 in the system of FIGS. 1Aand 1B for substantially in-phase side-to-side welding waveforms withabout zero degree waveform phase angle Φ. As shown in the plot 80, theexemplary welding system 2 is operable to provide synchronized first andsecond welding waveforms 81 and 82 via the power sources 24 a and 24 b,respectively, wherein the waveform synchronization can be by anysuitable means in the system 2, such as the synchronizing controller 40or other system component, whether hardware, software, or combinationsthereof. In one preferred embodiment, the system 2 is employed inperforming a dual fillet DC pulse welding process using flux coredelectrodes E1 and E2, as exemplified in FIGS. 1A, 1B, 2B, and 3-6,wherein the temporally aligned DC pulse waveforms 81 and 82 of FIG. 7Amay be provided to perform the dual fillet welding. As shown in the plot80 of FIG. 7A, moreover, the DC pulse waveforms 81 and 82 aresubstantially in-phase with zero waveform phase angle Φ, so as tofacilitate control over the consistency and symmetry of the weldpenetration. In this implementation, both the DC pulse welding waveforms81, 82 are comprised of a series of pulses including a backgroundcurrent level I_(B) and a higher pulse current level I_(P), with thepulses of the first and second welding currents I₁ and I₂ beingsubstantially in phase, such as within about 10 electrical degrees ofone another, wherein the relative waveform phase angle Φ in this case isabout zero, such as about 10 degrees or less. In the illustratedexample, moreover, the first and second waveforms 81 and 82 aresubstantially identical, although not a requirement of the invention. Inthis regard, one possible application of this type of implementation iswhere the first and second welds W1 and W2 are desired to be the samesize, with equal or similar weld leg dimensions 64 and 65 on both sidesof the stiffener workpiece WP1.

While the current waveforms are illustrated in the DC pulse weldingexamples of FIGS. 7A-7C as having less than a 50% duty cycle (the ratioof the pulse current time divided by the background current time), thewaveforms may be of any suitable duty cycle to implement a given dualfillet welding procedure. Furthermore, the implementation shown in FIG.7A provides for substantially equal pulse current values I_(P1) andI_(P2), as well as substantially equal background current levels I_(B1)and I_(B2) in the two waveforms. However, other embodiments may providedifferent waveform values, wherein I_(P1) need not equal I_(P2) and/orwhere I_(B1) and I_(B2) may be unequal, for instance, where differentelectrode diameters are used in the machines 20 a and 20 b, and/or wheredifferent first and second weld sizes are desired.

In certain embodiments, the power sources 24 are provided withsynchronization information, such as heartbeat signals, messages, etc.,from the synchronizing controller 40 (FIG. 1), with the waveformgenerators of the power sources 24 operating to create the first andsecond welding currents I₁ and I₂ at the controllable waveform phaseangle Φ. In this fashion, with the waveform phase angle Φ at about zeroin FIG. 7A, the pulse current levels I_(P1) and I_(P2) of the first andsecond currents I₁ and I₂ are substantially aligned in time, and thecurrents are at the background levels I_(B1) and I_(B2) substantiallyconcurrently. In this manner, the penetration of the resulting filletwelds W1 and W2 can be controlled to achieve generally symmetricalpenetration for welds of the same size, as well as consistent weldpenetration values along the length of the welds.

In other embodiments where the weld sizes are desired to be different(e.g., using different first and second pulse levels I_(P1) and I_(P2)and/or different background levels I_(B1) and I_(B2)), the temporalsynchronization of the first and second waveforms 81 and 82 facilitatesconsistency of the weld penetration along the weld length, even wherethe welds W1 and W2 may penetrate by different amounts. In anotherpossible embodiment, the pulse and/or background levels may be differentfor the first and second welding waveforms 81 and 82, where theelectrodes E1 and E2 are not the same, such as different diameter wires,different materials, etc., where the desired weld sizes, profiles, etc.,may be the same, and where the wire feed speeds may, but need not, beequal. The synchronization of the welding waveforms 81 and 82 in theseimplementations may also advantageously facilitate control of the weldpenetration consistency along the weld length, in addition to enablingsubstantially symmetrical penetration on the two sides of the stiffenerWP1. Thus, the waveform synchronized system 2 may be employed to providesignificant advantages in terms of weld consistency, weld strength, andwelding costs in a variety of possible dual fillet welding applicationsthrough the controlled provision of the first and second welding currentwaveforms substantially in phase, as exemplified in the plot 80 of FIG.7A and variants thereof. In addition, it is noted that while theillustrated DC pulse waveforms 81 and 82, and the AC waveforms of FIGS.14A-14C below, are generally square wave pulse waveforms, other waveformshapes are contemplated, wherein the illustrated embodiments are merelyexamples.

This aspect of the invention also provides for other controlled waveformphase angle values Φ. FIG. 7B illustrates a graph 84 showing exemplaryfirst and second DC pulse welding current waveforms 85 and 86,respectively, with a controlled non-zero degree waveform phase angle Φ,and FIG. 7C provides a graph 87 illustrating first and second weldingcurrent waveform plots 88 and 89 for substantially out-of-phase weldingwaveforms with about 180 degree waveform phase angle. In the case ofFIG. 7C, the magnetic effects of the two pulse welding arcs will besubstantially out-of-phase for waveform phase angles Φ of about 180degrees, such as 175 to 185 degrees, thereby allowing control over thedual fillet weld uniformity, penetration, shape, size, etc. through thecontrolled waveform synchronization in the system 2.

Referring also to FIGS. 7D-7G, further aspects of the invention involvecontrolled modulation of workpoints according to a waveform associatedwith the welding machines 20 a and 20 b in a manner to provide acontrolled workpoint phase angle between the machine workpointwaveforms. The machine workpoints can be provided and modulated in oneembodiment by the workpoint allocation system 12 (FIG. 18), where theworkpoints are provided to the machines 20 in some variable manner toestablish a waveform, such as a square wave, sine wave, ramps, or anyother waveform shape. In another possible embodiment, the machineworkpoint modulation is controlled by the synchronizing controller 40.Other embodiments are possible, where the workpoint modulation isprovided by cooperative interaction of the workpoint allocation system12 and the synchronizing controller 40 or by any other single element ofthe welding system 2 or combination of system elements, or by anexternal component operatively connected to the welding system 2, suchas components communicatively coupled with the welding system 2 vianetworks, whether wired or wireless, etc.

One example is shown in FIG. 7D, in which a graph 90 illustratesexemplary plots 90 a-90 d of synchronized square-wave type weldingmachine wire feed speed and power source output workpoint valuewaveforms in the system 2 for substantially out-of-phase machineoperation at a workpoint phase angle α of about 180 degrees, such as 175to 185 degrees. Any suitable relative phase angle α can be used, whereinthe invention is not limited to substantially out-of-phase operations asshown in the example of FIG. 70. As shown in this embodiment, the firstmachine workpoint value is provided (e.g., by the workpoint allocationsystem 12 in one embodiment) as either a wire feed speed (WFS₁) or apower sourced output value (Power Source Output₁) from which the firstmachine 20 a derives the other. In the illustrated example, the firstmachine workpoint value is modulated over time by the workpointallocation system 12 in the form of a square wave waveform having aperiod T with the first wire feed speed value 90 a alternating between ahigh value WFS_(1a) and a low value WFS_(1b), wherein the first powersource output 90 b tracks this square waveform with high and low outputvalues Power Source Output_(1a) and Power Source Output_(1b),respectively, aligned with the high and low WFS values WFS_(1a) andWFS_(1b). The workpoint allocation system 12 also provides a secondmachine workpoint to the second welding machine 20 b, such as a wirefeed speed (WFS₂) or a power sourced output value (Power SourceOutput₂), where the second wire feed speed machine workpoint value 90 calternates between a high value WFS_(2a) and a low value WFS_(2b), andthe second power source output 90 d tracks this square waveform of thesame period T with high and low output values Power Source Output_(2a)and Power Source Output_(2b), respectively. In accordance with certainaspects of the present invention, moreover, the first and second machineworkpoint values are modulated according to first and second machineworkpoint waveforms to provide a controlled machine workpoint phaseangle α between the first and second machine workpoint waveforms, whichcan be any value, such as about 180 degrees for substantiallyout-of-phase operation of the opposing welding operations in theillustrated example.

By controlling the workpoint phase angle α, the allocation system 12 cancontrol the size, uniformity, consistency, etc. of the resulting dualfillet weld while achieving an overall desired system output. In thisregard, the workpoint allocation system 12 (FIG. 1B) receives a userselected system workpoint value and provides the modulated first andsecond machine workpoint values to the welding machines 20,respectively, based on the system workpoint value to set a total outputof the multiple arc welding system 2 to the system workpoint value,wherein the system workpoint value can be any suitable value, parameter,measure, etc. associated with the system 2 or the dual fillet weldingprocess, including but not limited to a system deposition rate, a weldsize, a wire feed speed, a welding current, a welding voltage, a travelspeed, etc. In implementing the desired system-wide performanceaccording to the user selected system workpoint, the workpointallocation system 12 provides any suitable form of machine workpoints tothe machines 20, including but not limited to a power source outputvalue, a waveform frequency, and a wire feed speed. In practice,moreover, the workpoint value modulation waveforms may be modulated atany suitable period T and corresponding frequency, such as about 0.1 toabout 10 Hz in one example, whereas the power source current outputwaveforms are generally of a much higher frequency, such as about 60-300Hz for pulse welding and about 20-90 Hz for AC welding, although thesefrequency values are merely examples and do not represent limitations toor requirements of the invention. In addition, it is noted that wherethe machines 20 are themselves synergic, the workpoint allocation system12 (or other system element) may provide a single machine workpoint toeach machine 20 (from which the machine 20 will derive two or moreworkpoints such as power source output value, a waveform frequency, anda wire feed speed, etc. Alternatively, the workpoint allocation system12 may provide more than one machine workpoint to one or both of themachines 20 or components thereof (e.g., a WFS workpoint to a wirefeeder 26 and a power source output value and/or frequency to the powersource 24), wherein the provided machine workpoint values may beadvantageously modulated according to various aspects of the invention.

FIG. 7E illustrates another possible workpoint modulation waveformwherein a graph 91 shows synchronized rounded wire feed speed and powersource output workpoint value waveform plots 91 a-91 d in the system 2,again at an exemplary workpoint phase angle α of about 180 degrees. Inthis case, the first and second wire feed speed workpoint values 91 aand 91 c provide a smoother transition between the high and low values,thereby allowing for mechanical time constants associated with wire feedmechanisms, wherein the power source output workpoint waveforms 91 and91 d also provide for rounded waveform transitions in concert with thecorresponding wire feed speeds. FIG. 7F shows a graph 93 withsynchronized ramped wire feed speed and power source output workpointvalue waveform plots 93 a-93 d also illustrated at a workpoint phaseangle α of about 180 degrees with all the waveforms operating at anexemplary period T. As another example, the graph 95 of FIG. 7Gillustrates synchronized sinusoidal wire feed speed and power sourceoutput workpoint value waveforms 95 a-95 d in the system 2, where thewaveforms 95 are each at a period T and the waveforms of the firstmachine 20 a are offset from those of the second machine 20 b by aworkpoint phase angle α, again about 180 in this example.

FIG. 8 illustrates another embodiment of the dual fillet welding system2, wherein the system includes a travel controller component 50operatively coupled with the welding system controller 10, along with atravel mechanism 52, such as a robot or other mechanical actuationsystem, to controllably translate a fixture 30 to guide the weldingelectrodes E1 and E2 along the welding direction 60 to perform the dualfillet welding process forming the welds W1 and W2 concurrently. Thetravel mechanism 52 can be any system that controls the spatialrelationship between the workpieces WP1 and WP2 and the electrodes E1and E2 to implement a dual fillet welding operation, and the associatedtravel controller 50 may be hardware, software, etc., whether separateor integrated or distributed within one or more system components, whichcontrols operation of the travel mechanism 52. In this regard, FIG. 8Ashows an alternate configuration with the travel mechanism 52 operativeto translate the workpieces WP1 and WP2 on a movable carriage or fixture30 a in the direction 60 relative to a fixed fixture 30 and stationarywelding torches.

As best shown in FIGS. 1B and 8, the exemplary system controller 10includes the synchronizing controller 40 and the workpoint allocationsystem 12, where the system controller 10 may be a stand alone componentwithin the overall dual fillet welding system 2, or one or morecomponents of the controller 10 may be integrated within or distributedamong one or more of the welding machines 20 or other system components.In one possible implementation, the welding machines 20 a and 20 b mayeach include system controller components 10, for example, within thepower sources 24 thereof, with one machine 20 being designated (e.g.,programmed or configured) to operate as a master and the otherconfigured to operate as a slave. In this type of embodiment, the mastermachine 20 is operatively coupled with the slave machine 20 to providethe system control functions as set forth herein. In this regard, thesystem controller 10, as well as the workpoint allocation system 12 andsynchronizing controller 40 thereof may be implemented in any suitableform, including hardware, software, firmware, programmable logic, etc.,and the functions thereof may be implemented in a single systemcomponent or may be distributed across two or more components of thewelding system 2. The workpoint allocation system 12 is operativelycoupled with the first and second welding machines 20, and receives auser selected system workpoint value 14, for example, a setting of auser accessible knob 18 or a signal or message from another input deviceor from a source external to the system 2, wherein the workpointallocation system 12 provides first and second welding machine workpointvalues to the machines 20 a and 20 b, respectively, based on the systemworkpoint value 14. Moreover, the workpoint allocation system 12 can beconfigured to modulate the provided machine workpoint values accordingto corresponding waveforms to provide the controlled workpoint waveformphase angle relationship for improved control of the dual fillet weldingoperation. Whether modulated or not, the workpoint allocation system 12provides the machine workpoint values so as to effectively set a totaloutput of the dual fillet welding system 2 in accordance with the systemworkpoint 14. In this manner, the system 12 allows a user to make asingle synergic adjustment from which the various operational parametersof the components in the welding system 2 are configured.

The system controller 10 may provide other control functions in thewelding system 2, such as data acquisition, monitoring, etc., inaddition to the workpoint allocation and synchronization functions, andmay provide various interface apparatus for interaction with a user(e.g., a user interface with one or more value adjustment apparatus suchas knobs 18, switches, etc., and information rendering devices, such asgraphical or numeric displays, audible annunciators, etc.), and or fordirect or indirect interconnection to or with other devices in adistributed system, including but not limited to operative connectionfor communications and/or signal or value exchange with the machines 20or other welding equipment forming a part of the system 2, and/or withexternal devices, such as through network connections, etc., whether forexchanging signals and/or communications messaging, including wire basedand wireless operative couplings. As best shown in FIG. 8, systemcontroller 10 receives a user selected system workpoint value 14, whichmay be obtained by a user adjusting one or more knobs 18 on a faceplateinterface of system controller 10, or which may be obtained from anotherdevice, for example, from a hierarchical controller or user interfacecoupled with system 2 through a network or other communicative means,whether wired, wireless, or other form (not shown). The systemcontroller 10 may also store and/or be operative to receive userselected process information 16, for example, process type information,welding electrode size information, process recipes or procedures, etc.

The workpoint allocation system 12 derives welding machine workpointvalues (e.g., wire feed speed values WFS1 and WFS2 in FIG. 8) for theindividual welding machines 20 based on the system workpoint value 14,wherein the derivation of the machine workpoints may, but need not, takeinto account user selected information 16 regarding a specific desiredor selected welding process or operation. The user selected processinformation 16 may specify, for example, whether a given process is tobe a dual fillet DC pulse process using flux cored electrodes E, asexemplified in FIGS. 1, 28, and 3-7C above, or an AC solid wire dualfillet submerged arc process as shown in FIGS. 10-14C below. Theworkpoint allocation functions may be implemented in any suitablefashion, including but not limited to lookup tables to map user selectedsystem workpoint values 14 to machine workpoint values, taking intoaccount welding process type and wire diameter and/or other processparameters (e.g., information 16), as well as algorithmic or equationbased computation of the machine workpoints based on the user selectedsystem workpoint value 14. In the implementation depicted in FIG. 8, forexample, the workpoint allocation system 12 receives the systemworkpoint 14, such as a deposition rate, a weld size, a wire feed speed,a welding current, a welding voltage, a travel speed, etc., and derivestwo or more machine workpoint values, such as wire feed speeds,deposition rates, welding currents, welding voltages, travel speedsetting for the travel controller 50, etc. according to a single systemworkpoint value 14. In this manner, the synergic workpoint allocationsystem 12 divides or apportions the system setting 14 into the weldingmachine workpoint values for the individual machines 20, wherein thesystem workpoint value 14 and the derived machine workpoint values may,but need not, be of the same type. For example, the user selected value14 may be a total system deposition rate expressed in units of poundsper hour, with the machine workpoints being wire feed speeds or othervalues. In this regard, the allocation system 12 in one embodiment mayprovide approximately equal first and second wire feed speed machineworkpoint values WFS1 and WFS2 to the machines 20 a and 20 b,respectively, in applications in which symmetrical welds W1 and W2 ofequal sizes are desired. The machines 20 or components thereof (e.g.,power sources 24) may derive further component settings from a singlemachine workpoint value, such as the power source 24 receiving a machinewire feed speed and deriving welding signal parameters therefrom (e.g.,voltage, current, pulse widths, duty cycles, etc), in localized synergicfashion, or the allocation system 12 may provide multiple workpoints toeach machine 20. Moreover, the workpoint allocation system 12 in theillustrated embodiment of FIG. 8 also derives at least one travelcontrol value (e.g., travel speed) based on the system workpoint value14 and provides the travel control value to the travel controller 50.

Referring also to FIG. 9, further details of the exemplary waveformcontrolled first power source 24 a are illustrated, wherein the secondpower source 24 b may be similarly constructed in certain embodiments ofthe welding system 2. In general, the system 2 may employ any switchingtype welding power source 24 that provides an electrical welding signalaccording to one or more switching signals. The exemplary source 24 aincludes a rectifier 150 that receives single or multiphase AC inputpower and provides a DC bus output to a switching inverter 152. Theinverter 152 drives an output chopper 154, where chopper 154 andinverter 152 are operated according to switching signals from a pulsewidth modulation (PWM) switching control system 168 to provide a weldingoutput signal at terminals 25 a suitable for application to a filletwelding process or operation. In practice, one or both of the outputterminals 25 a may be coupled through a power source cable to wirefeeder 26 a for ultimate provision of the welding signal to the weldingoperation through a torch and cable (not shown), where welding currentand voltage sensors 172 and 174 are provided in power source 24 tocreate feedback signals for closed loop control of the applied weldingsignal waveform 81. Power source 24 a also includes a waveformgeneration system 160 providing switching signals to the output chopper154 and optionally to inverter 152, where system 160 includes a waveformgenerator 162 providing a desired waveform control signal to an input ofa comparator 168 according to a selected desired waveform 164, stored asa file in one example. The desired waveform is compared to one or moreactual welding process conditions from a feedback component 170 and thecomparison is used to control the PWM switching system 168 to therebyregulate the welding signal in accordance with the desired waveform(e.g., welding current signal waveform 81 of FIG. 7).

The waveform generation system 160 in the embodiment of FIG. 9 and thecomponents thereof are preferably implemented as software or firmwarecomponents running in a microprocessor based hardware platform, althoughany suitable programmable hardware, software, firmware, logic, etc., orcombinations thereof may be used, by which one or more switching signalsare created (with or without feedback) according to a desired waveformor waveform file 164, wherein the switching type power source 24 aprovides a welding signal according to the switching signal(s). Onesuitable power source is shown in Blankenship U.S. Pat. No. 5,278,390,wherein the power source 24 a can be a state table based switching powersource that may receive as inputs, one or more outputs from other systemcomponents, such as a sequence controller, the welding system controller10, etc., wherein waveform generation system components 162, 166, 170may be implemented as a waveform control program running on, or executedby, a microprocessor (not shown) that defines and regulates the outputwaveform of power source 24 a by providing control signals via PWMsystem 168 to inverter 152 and/or chopper 154, where the output waveformcan be a pulse type of any waveform or shape that can be synchronizedfor substantially in-phase operation relative to a second power source24, and may provide for DC or alternative current polarities (AC), asshown in the submerged arc embodiment of FIGS. 10-14 below.

Referring now to FIGS. 10-14D, another possible embodiment of thewelding system 2 is illustrated, in which solid wire electrodes E1 andE2 (FIG. 2A above) are employed in a submerged arc dual fillet weldingprocess with synchronized AC pulse welding waveforms that are at acontrolled waveform phase angle relationship or synchronized workpointvalue modulation. FIG. 14A shows a plot 180 depicting exemplary firstand second AC pulse welding current waveforms 181 and 182, respectively,each comprising a series of pulses including a positive current levelI_(P) and a negative current level I_(N), with the pulses of the firstand second welding currents being substantially in phase with oneanother at a controlled waveform phase angle α of about 0+/−5 degrees.Another example is shown in the graph 190 of FIG. 148, wherein the firstand second current waveforms 191 and 192 are operated at the samefrequency, but the waveforms thereof are temporally offset by a non-zerowaveform phase angle α. Yet another example is shown in the graph 195 ofFIG. 14C, in which the power source output current waveforms 196 and 197are substantially out-of-phase with the relative waveform phase angle αbeing about 180 degrees (e.g., 175-185 degrees in one embodiment). It isappreciated that the various AC current and/or voltage waveforms outputby the machine power sources 24 may be of any form or shape and need notbe the same, wherein the figures are merely examples and are notrequirements or limitations of the invention. As with the abovedescribed DC pulse examples, moreover, the phase controlled AC waveforms181 and 182 can be employed to control the consistency and symmetry ofthe weld penetration of the opposing welding electrodes E1 and E2 duringconcurrent dual fillet welding, wherein the illustrated embodiment ofFIGS. 10-13 employs the AC waveform control in combination withrelatively large diameter solid electrodes E (FIG. 2A) and granular fluxF (FIGS. 10 and 11) in a submerged arc welding (SAW) process. Thewaveforms 181 and 182 each include a series of pulses having positiveportions (I_(P1) and I_(P2)) and negative portions (I_(N1) and I_(N2)),illustrated as currents 11 and 12 in FIG. 14A-14C, wherein the pulses ofthe first and second welding currents 11 and 12 are synchronized by thesynchronizing controller 40 to provide a controlled or regulatedwaveform phase angle α (e.g., within about +/−5 electrical degrees ofthe target angle value α in one embodiment).

In one preferred embodiment, moreover, the first and second waveforms181 and 182 are substantially identical as shown in the plot 180,although not a requirement of the invention. In addition, the exemplarywaveforms 181 and 182 are of approximately 50% duty cycle, althoughother embodiments are possible using any suitable duty cycle. Inaddition, while the illustrated waveforms are symmetric about the zerocurrent axis with /I_(P1)/ substantially equal to /I_(N1)/ and with/I_(P2)/ substantially equal to /I_(N2)/, other embodiments are possibleusing asymmetrical waveforms in this respect. Furthermore, the preferredembodiment of FIGS. 10-14C employ first and second waveforms 181 and 182that are substantially identical, although this is not a requirement ofthe invention. As with the above described dual fillet DC pulse weldingimplementations, moreover, the power sources 24 generate the ACsubmerged arc welding signal waveforms 181 and 182 in FIGS. 10-14 usingsynchronization information (e.g., heartbeat signals, messages, etc.)from synchronizing controller 40 (FIGS. 1, 8 and 9) to provide weldingcurrents 11 and 12 in a controlled phase angle relationship with respectto one another to facilitate improved control of the resulting filletwelds W1 and W2. As best shown in FIGS. 10-13, the dual fillet SAWprocess uses granular flux F (FIGS. 10 and 11) formed into two pilesalong the sides of the T-joint between the stiffener workpiece WP1 andthe base workpiece WP2, and the energized welding electrodes E1 and E2(FIG. 2A) are passed through the flux piles F. The current signalwaveforms 181 and 182 applied to the electrodes E1 and E2 establish andmaintain welding arcs A1 and A2 within the granular flux F, causing theflux F to melt and form slag S (FIGS. 10 and 12) over the molten weldsW1 and W2, as best shown in FIG. 11. The AC welding waveform ispreferably balanced with respect to the zero voltage axis and preferablyof a 50 percent duty cycle, wherein these preferred conditions cancontribute to controlled penetration and bead shape, although theseconditions are not strict requirements of the invention. The dual filletwelding process may lead to weld material W1 and/or W2 penetrating oneor both of the workpieces WP1 and WP2 through partial consumption ofworkpiece material and inclusion thereof into the welds W1, W2,resulting in lateral penetration dimensions 92 a and 92 b and/or firstand second downward penetration depths 94 a and 94 b. As the electrodesE are moved along the weld direction 60 (e.g., via travel mechanism 52of FIG. 8), the weld material W1, W2 solidifies beneath the slag S, andslag S also solidifies as shown in FIG. 12. The slag S is then removed,leaving the finished fillet welds W1 and W2 as shown in FIG. 13, whichare substantially the same in the illustrated embodiment. The inventionthus provides dual fillet welding systems and methods for dual filletwelding applications, in which the welding signals are synchronized forcontrolled phase angle operation to facilitate control over dual filletwelding system performance and finished weld quality.

Referring also to FIG. 14D, as discussed above, further aspects of theinvention provide for welding machine workpoint modulation at acontrolled phase relationship, which also finds utility in associationwith AC dual fillet welding applications, such as the submerged arcexample of FIGS. 10-12. FIG. 14D provides a graph 198 showing exemplaryfirst and second synchronized square-wave type welding machine wire feedspeed waveforms 198 a and 198 d, power source output waveforms 198 b and198 e, and welding frequency workpoint value waveforms 198 c and 198 fin the exemplary dual fillet welding system 2, wherein the workpointwaveforms 198 a-198 c of the first machine 20 a are modulated at aperiod T at a controlled workpoint phase angle α relative to themodulated workpoint waveforms 198 d-198 f of the second machineworkpoints, with all the workpoint modulation waveforms being operatedat a period T. In this example, moreover, the first and second machineworkpoints are modulated in a substantially out-of-phase manner with thea workpoint phase angle α at about 180 degrees, although any suitablecontrolled phase angle α may be employed. In this example, it is notedthat the power source operating frequencies (e.g., the frequencies ofthe power source output current/voltage waveforms) may also be modulatedin the workpoint modulation technique. In this example, the AC weldingwaveform frequency is varied in concert with the amplitude, wherein likethe above pulse welding examples, the modulation of the workpoints in ACapplications can be according to any suitable modulation waveformshapes, forms, etc., wherein the illustrated square wave workpointmodulation waveforms 198 a-198 f in FIG. 140 are merely examples.Further, the modulation waveforms of a given machine may be of similarshape, form, etc., as shown, or these may be different. Moreover, themodulated machine workpoint waveforms may be provided as a group to eachmachine 20, or the workpoint allocation system 12 (or other systemcomponent) may provide a single modulated workpoint to a machine 20 withthe machine 20 then deriving the remaining workpoints for the variousmachine components. In the example of FIG. 140, moreover, the powersource waveform output frequency of each machine is increased when thecorresponding wire feed speed and output amplitude is increased and viceversa.

Referring now to FIGS. 15A and 15B, the welding currents and wire feedspeeds of the welding machines 20 a and 20 b may be controlled toprovide controlled partial penetration of the T-joint as shown in FIGS.5 and 6 above, or to provide for essentially complete penetration of theweld joint as seen in FIGS. 15A and 15B, for pulse welding, AC welding,or other dual fillet welding type operations, wherein the waveformsynchronization and/or workpoint synchronization techniques describedabove can be used to facilitate controlled provision of any desiredamount and form of weld penetration for a given dual fillet weldingapplication. FIG. 15A illustrates an exemplary beveled stiffener firstworkpiece WP1 a used in forming a dual fillet welded T-joint includingbeveled lower surfaces 202 and 204 which may be used alone or incombination with one or both of the waveform or workpointsynchronization aspects of the invention to achieve dual fillet weldshaving substantially complete penetration to provide an overlap region20 where the first and second fillet welds W1 and W2 join beneath thefirst workpiece WP1 a as shown in FIG. 15B.

The above examples are merely illustrative of several possibleembodiments of various aspects of the present invention, whereinequivalent alterations and/or modifications will occur to others skilledin the art upon reading and understanding this specification and theannexed drawings. In particular regard to the various functionsperformed by the above described components (assemblies, devices,systems, circuits, and the like), the terms (including a reference to a“means”) used to describe such components are intended to correspond,unless otherwise indicated, to any component, such as hardware,software, or combinations thereof, which performs the specified functionof the described component (i.e., that is functionally equivalent), eventhough not structurally equivalent to the disclosed structure whichperforms the function in the illustrated implementations of theinvention. In addition, although a particular feature of the inventionmay have been disclosed with respect to only one of severalimplementations, such feature may be combined with one or more otherfeatures of the other implementations as may be desired and advantageousfor any given or particular application. Also, to the extent that theterms “including”, “includes”, “having”, “has”, “with”, or variantsthereof are used in the detailed description and/or in the claims, suchterms are intended to be inclusive in a manner similar to the term“comprising”.

In some exemplary embodiments, a hybrid laser system is used to createthe dual fillet welds. Use of a hybrid laser system allows for smallerweld bead size, faster travel speeds, and less distortion. This isbecause, by combining the focused energy of a laser beam with aconventional arc system to melt the base metal, the penetration of themolten puddle (i.e., weld puddle) is deeper than if just a conventionalarc-only system was used. For example, in the exemplary application ofwelding a T-joint, the hybrid laser system can provide full penetrationof the T-joint with a narrow heat-affected zone (HAZ). By preheating theworkpieces and getting a deeper penetration using the laser, the weldbead size can be considerably smaller while still achieving the same orbetter cross section of fused material as that of a fillet weld madewith a conventional arc-only system. For example, the weld bead size canbe in the range of 1 to 8 mm leg length ( 5/16 in fillet) in hybridlaser systems. In addition, due to the smaller bead size, less fillermaterial is needed and the T-joint can be fillet welded at travel speedsthat are higher than conventional arc-only systems, e.g., in a range of1.5 to 4 meters/min or 60 to 150 ipm travel speed. Further, becausethere is less molten metal using a laser process, there is lessdistortion than a conventional arc-only system.

Conventional systems are unable to take full advantage of the benefitsof hybrid laser welding when performing concurrent welds where the arcsare in close proximity. That is, although a hybrid laser system can beused when welding the fillet weld on one side of the T-joint, the otherside of the T-joint cannot have an arc directly across from the firstarc, as there will be magnetic interference from the two arcs in theconventional systems. If the second arc is positioned such that ittrails the first arc to minimize the magnetic interference, theadvantages due to the keyhole effect on the second side will be lostbecause the metal will cool off by the time the second arc travels overthe keyhole area. While it is possible to also use a hybrid laser systemon the second side, this would either double the manufacturing time orit would be expensive due to the second laser.

Unlike conventional systems, embodiments of the present invention cantake full advantage of the benefits of hybrid laser as discussed above.As seen in FIG. 16A, the hybrid laser system includes a high intensitylaser 300 that focuses a laser beam 310 onto the base of the T-jointformed by workpieces WP1 and WP2. The laser can be any type of highenergy laser source, including but not limited to carbon dioxide,Nd:YAG, Yb-disk, YB-fiber, fiber delivered or direct diode lasersystems. Further, even white light or quartz laser type systems can beused if they have sufficient energy. For example, a high intensityenergy source can provide at least 500 W/cm2. In addition, the lasershould have the ability to “keyhole” into the root metal of theworkpieces being welded. That is, the laser should have sufficientenergy to form a vapor cavity in the root metal that can extendsubstantially into the root, e.g., 60% to 100% of the thickness of theworkpiece WP1 in some embodiments and 95% to 100% of the thickness ofthe workpiece WP1 in other embodiments. In typical hybrid laserapplications, the workpiece thickness can range from 3 mm to 15 mm or ⅛inch to ½ inch. Of course, other thickness can be used based on therequirements of the application.

The hybrid laser system also includes welding systems, e.g., GMAWsystems, that include power supplies 430 and 440 supplying weldingcurrent to wires 330 and 335 via torches 320 and 325, respectively. Thewelding currents create arcs 303 and 304 between consumable electrodes(wires) 330 and 335, respectively, and the workpieces WP1 and WP2. EachGMAW system can also include shielding gas (not shown) for protectingthe weld zone from atmospheric contamination. Although the exemplaryembodiments will be described in term of GMAW systems, the presentinvention can also be used with TIG, PAW, SAW, FCAW-S, FCAW-G, and MCAWsystems. The arcs 303 and 304 deposit material from consumableelectrodes (wires) 330 and 335 to form fillet welds 301 and 302,respectively, at the root of the T-joint. As in the exemplaryembodiments discussed above with respect to FIGS. 1-15, the torches 320and 325 (see FIG. 16B) can be positioned such that their respective arcs303 and 304 are directly across from each other on opposite sides of theweld, which in this case will be on opposite sides of workpiece WP1. TheGMAW systems are configured to concurrently weld both sides of theT-joint as the torches 320 and 325 travel down the T-joint (see arrow inFIG. 16B). As in the exemplary embodiments discussed above, the magneticfield interference caused by the welding currents through arcs 303 and304 can be controlled by synchronizing the welding waveforms output fromthe welding power supplies 430 and 440. For example, the phase angle ofthe welding currents relative to one another can be shifted to minimizethe magnetic interference. In some exemplary embodiments, the weldingwaveform at torch 325 is shifted such that the welding current pulses attorch 325 are not in phase with the welding current pulses at torch 320.For example, the welding waveform at torch 325 can be shifted byapproximately 180 degrees with respect to the waveform at torch 320,e.g., in a range between 175 to 185 degrees. Of course, in otherembodiments, the phase angle can be in a range between 90 to 270degrees. By synchronizing the welding currents such that the respectivepeak currents are not in phase, e.g., by being shifted by approximately180 degrees, the magnetic fields from arcs 303 and 304 have minimalinfluence on each other, thus allowing the arcs 303 and 304 to bedirectly across from each other on opposite side of the weld (workpieceWP1). Synchronizing the welding waveforms, including shifting waveformsby a phase angle, in order to minimize magnetic interference isdisclosed above and therefore will not be discussed in detail except asnecessary to explain the present exemplary embodiments.

As seen in FIG. 16B, the laser beam 310 is focused just ahead of arcs303 and 304 on, e.g., the arc 303 side with respect to the direction oftravel in order to create a keyhole at the root of the T-joint. Thedistance D between the laser beam 310 and the arcs 303 and 304 should besuch that the metal does not cool appreciably before the arcs 303 and304 travel over the keyhole area. For example, the distance D betweenthe centerline of the laser beam 310 and the arc 303 can be in a rangeof 1 to 5 mm. The laser beam 310 forms a keyhole that extendssubstantially to the opposite side of workpiece WP1, e.g., the keyholecan extend in a range of, e.g., 95% to 100% of the thickness of WP1, andcan also extend into the base workpiece WP2 to further promote a goodfusion between the workpieces WP1 and WP2. Thus, the keyhole extends farenough into workpieces WP1 and WP2 such that the root of the T-joint onthe arc 304 side is also affected. Thus the laser helps to preheat forthe arcs allowing the arcs to wet out sufficiently to achieve a smoothtransition with minimal bead size. Accordingly, due to the keyhole andthe minimal magnetic interference on the arcs 303 and 304, embodimentsof the present invention can concurrently create the fillet welds 301and 302 with a small bead size and with good fusion.

In some embodiments, as illustrated in FIG. 17, the laser power supply420 is controlled by a hybrid system controller 450 that can alsocontrol the welding power supplies 430 and 440 and the wire feeders 460and 470. The hybrid system controller 450 includes programs that performthe functions of welding system controller 10 discussed above, e.g., theduel fillet welding operation. The hybrid system controller 450 can alsoinclude programs that control laser functions such as, e.g., controllingthe focus for a keyhole, wire feeder functions such as, e.g.,controlling the wire feed speed, and shielding gas functions such ascontrolling the flow of gas to the torches 320 and 325. Of course,instead of an integrated approach, one or more the power supplies,feeders, and systems can be controlled independently of the controller450.

In some embodiments, the hybrid system controller 450 operativelyinterfaces to the welding power supplies 430 and 440 and the laser powersupply 420 in order to synchronize and coordinate their outputs. Ofcourse, the hybrid system controller 450 can also synchronize andcoordinate the operation of the wire feeders 460 and 470 and theshielding gas (not shown). In some embodiments, the hybrid systemcontroller 450 can be a parallel state based controller, e.g., asillustrated in FIG. 17, and include state tables 455 that execute thesteps associated with controlling the associated power supplies andequipment. Parallel state-based controllers are disclosed and taught inapplication Ser. Nos. 13/534,119 and 13/438,703, which are incorporatedby reference herein in their entirety. Accordingly, state controllersand state tables will not be discussed in detail except as necessary toexplain the present invention.

The hybrid system controller 450 can include states tables 455 thatcontrol the operation of power supplies 430 and 440 such that, e.g.,they output the synchronized DC pulse welding current waveformillustrated in FIG. 7C. For example, one of the power supplies 430 and440 can output a welding current 88 (see FIG. 7C) and the other powersupply outputs a welding current 89 whose phase is shifted byapproximately 180 degrees with respect to 88. In some embodiments, thewelding currents 88 and 89 can be pulse spray transfer waveforms. Tosynchronize the waveforms 88 and 89, state table 455 for at least one ofthe power supplies can transmit a synchronization signal to the otherpower supply such that the phase angle of the welding currents can besynchronized. Of course, the present invention is not limited to pulsespray transfer waveforms and other welding waveforms can be used suchas, surface tension transfer (STT), shorted retract welding, etc. Inaddition, the two waveforms can be the same (e.g., both pulse spraytransfer or STT) or different (e.g., one is pulse spray and the other isSTT) as desired. Further, the present invention is not limited to aphase shift of 180 degrees and the phase difference between the twowelding current waveforms can be, e.g., 90 to 270 degrees. That is, inexemplary embodiments, the phase difference is such that the weldingcurrent pulses at torch 325 are not in phase with the welding currentpulses at torch 320.

The hybrid system controller 450 can also include a state table 455 thatcontrols the operation of laser power supply 420. For example, the statetable 455 for the laser power supply 420 can control the set up suchthat the joint is placed at the focal point of the laser. This creates akeyhole through the joint interface, thus fusing it together. Thelaser's intensity is such that the base metal cannot pull or transferthe heat away before the GMAW systems can use it as preheat. Parameterssuch as focus can be controlled to obtain a desired spot size and thuskeyhole characteristics. The control of laser power supply 420 and thewelding power supplies 430 and 440 can be coordinated by hybridcontroller 450 (or some other device) such that the welding method isoptimized.

In some embodiments, the hybrid system controller 450 can receivefeedback signals from the laser power supply 420, e.g., feedback relatedto the laser output intensity, optical focus, actual laser power, etc.In addition to, or alternatively, the feedback signals can include datafrom sensor 510 that monitors the temperature of the molten puddle atthe keyhole (or an area adjacent to the keyhole). The sensor 510 can bea type that uses a laser or infrared beam, which is capable of detectingthe temperature of a small area—such as the molten puddle or an areaaround the puddle—without contacting the puddle or the workpiece WP1.The feedback from the laser power supply 420 and/or the sensor 510 canbe used by hybrid system controller 450 to control the power level,optical focus, etc. to maintain a desired temperature at the keyhole.Similarly, the hybrid system controller 450 can receive feedback signalsfrom the power supplies 430 and 440, e.g., feedback related to therespective arc voltages, welding currents, power levels, etc.

In accordance with an embodiment of the present invention, the synergiccontrol of the arc welding power sources discussed above can be adaptedto include a laser. With a single point of control, functions of powersupplies 430 and 440 and the laser power supply 420 are combined into aunified process. As such, adaptive controls that respectively regulate aconsistent arc length for arcs 303 and 304 may include the power levelof laser 300. For example, the arc length(s) may be regulated byadapting the laser waveform. In general, it is desirable to maintain aconstant arc length (and, therefore, a constant arc voltage) for aselected wire feed speed. If arc voltage deviates from the desiredlevel, then the laser may be used to, for example, add heat to the arcwelding process such that arc voltage of power supply 430 and/or powersupply 440 can be brought back into control.

In some embodiments, arc welding current, arc welding voltage, and wirefeed speed from each GMAW system and the laser power level can all becontrolled as an integrated system. For example, controlling the wirefeed speed in one system can also automatically adjust arc weldingcurrent levels and/or durations, arc welding voltage levels and/ordurations, and laser power levels and/or durations based on predefinedrelationship tables of such parameters in the hybrid system controller450 (or some other device). Such tables may be tied to wire material andwire diameter also.

It should be noted that although GMAW systems are shown and discussedregarding depicted exemplary embodiments, exemplary embodiments of thepresent invention can also be used with TIG, PAW, FCAW-C, FCAW-S, MCAW,and SAW systems. In addition, a hot wire can also be fed to the back ofthe arc. Further, although a T-joint is shown and discussed regardingdepicted exemplary embodiments, exemplary embodiments of the presentinvention can be used in hybrid welding applications that use two ormore arcs in close proximity. e.g., a butt joint with reinforcement onboth sides.

1. (canceled)
 2. A method for hybrid welding a dual fillet weld, saidmethod comprising: providing a laser beam that leads a first torch andpreheats at least one of a first workpiece and a second workpiece;supplying a first welding waveform to a first wire via said first torchto form a first arc between said first wire and at least one of saidfirst workpiece and said second workpiece; supplying a second weldingwaveform to a second wire via a second torch to form a second arcbetween said second wire and at least one of said first workpiece andsaid second workpiece; synchronizing said first welding waveform andsaid second welding waveform such that welding current pulses of saidsecond welding waveform at said second torch are not in phase withwelding current pulses of said first welding waveform at said firsttorch; and disposing said first torch and said second torch such thatsaid first arc and said second arc are across from each other onopposite sides of a weld between said first workpiece and said secondworkpiece.
 3. The method of claim 2, further comprising: shifting aphase angle between said welding current pulses of said first weldingwaveform said welding current pulses of said second welding waveform soas to control magnetic interference between said first arc and saidsecond arc.
 4. The method of claim 2, further comprising: shifting aphase angle between said welding current pulses of said first weldingwaveform and said welding current pulses of said second welding waveformto be in a range between 90 to 270 degrees.
 5. The method of claim 4,wherein said range is between 175 to 185 degrees.
 6. The method of claim2, further comprising: regulating at least one of an arc length of saidfirst arc and an arc length of said second arc by controlling at least apower level if said laser beam.
 7. The method of claim 2, furthercomprising: creating a keyhole in said at least one workpiece.
 8. Themethod of claim 2, wherein said first workpiece and said secondworkpiece are disposed such that said first workpiece and said secondworkpiece form a T-joint, and wherein said weld comprises fillet weldson each side of said T-joint.
 9. The method of claim 8, furthercomprising: creating a keyhole in a base of said T-joint, wherein saidkeyhole extends in a range of 60 to 100 percent of a thickness of saidT-joint.
 10. The method of claim 8, further comprising: concurrentlywelding said fillet welds on each side of said T-joint.
 11. A method forhybrid welding a dual fillet weld, said method comprising: providing alaser beam that leads a first torch and preheats at least one workpiece;supplying a first welding waveform to a first wire via said first torch,said first welding waveform creating a first arc between said first wireand said at least one workpiece; supplying a second welding waveform toa second wire via a second torch, said second welding waveform creatinga second arc between said second wire and said at least one workpiece;synchronizing said first welding waveform and said second weldingwaveform such that welding current pulses of said second weldingwaveform at said second torch are not in phase with welding currentpulses of said first welding waveform at said first torch; disposingsaid first torch and said second torch such that said first arc and saidsecond arc are across from each other on opposite sides of a weld; andsetting a distance between a centerline of a laser beam from said lasersystem and said first arc is to be in a range of 1 to 5 mm.